Loans and Leases and the Allowance for Credit Losses - Loan Modification Activities that were Considered Troubled Debt Restructurings (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) Modification	Sep. 30, 2015 USD ($) Modification	Sep. 30, 2016 USD ($) Modification	Sep. 30, 2015 USD ($) Modification
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	134	245	569	613
Pre-modification, Recorded investment	$ 93,640	$ 23,691	$ 235,214	$ 139,888
Post-modification, Recorded investment	83,898	23,657	224,499	137,646
Financial effects of modification, Recorded investment	(9,742)	(34)	(10,715)	(2,242)
Financial effects of modification, Interest	$ (599)	$ (557)	$ (1,627)	$ (1,406)
Principal Deferral [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	14	15	40	37
Pre-modification, Recorded investment	$ 12,302	$ 4,230	$ 18,511	$ 47,005
Post-modification, Recorded investment	11,644	4,208	17,802	45,569
Financial effects of modification, Recorded investment	$ (658)	$ (22)	$ (709)	$ (1,436)
Principal Deferral [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	30	36	87	87
Pre-modification, Recorded investment	$ 41,652	$ 7,893	$ 98,956	$ 25,483
Post-modification, Recorded investment	40,183	7,419	98,561	24,331
Financial effects of modification, Recorded investment	$ (1,469)	$ (474)	$ (395)	$ (1,152)
Principal Deferral [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	21	31	46	50
Pre-modification, Recorded investment	$ 4,489	$ 3,540	$ 7,433	$ 4,954
Post-modification, Recorded investment	4,714	3,743	7,945	5,239
Financial effects of modification, Recorded investment	$ 225	$ 203	$ 512	$ 285
Principal Deferral [Member] | Residential Limited Documentation [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	3	1	6	2
Pre-modification, Recorded investment	$ 435	$ 265	$ 711	$ 426
Post-modification, Recorded investment	470	276	803	437
Financial effects of modification, Recorded investment	$ 35	$ 11	$ 92	$ 11
Principal Deferral [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	4	4	8	6
Pre-modification, Recorded investment	$ 251	$ 727	$ 655	$ 1,946
Post-modification, Recorded investment	$ 251	$ 727	$ 655	$ 1,946
Principal Deferral [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	10	35	102	133
Pre-modification, Recorded investment	$ 186	$ 316	$ 865	$ 1,234
Post-modification, Recorded investment	$ 186	$ 316	$ 865	$ 1,234
Principal Deferral [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	1	24	56	73
Pre-modification, Recorded investment	$ 26	$ 352	$ 951	$ 1,418
Post-modification, Recorded investment	$ 26	$ 352	$ 951	$ 1,418
Principal Deferral [Member] | Other Commercial Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		3	1	3
Pre-modification, Recorded investment		$ 296	$ 250	$ 296
Post-modification, Recorded investment		390	$ 250	390
Financial effects of modification, Recorded investment		$ 94		$ 94
Principal Deferral [Member] | Residential Builder and Developer [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification			3	2
Pre-modification, Recorded investment			$ 23,905	$ 10,650
Post-modification, Recorded investment			22,958	10,598
Financial effects of modification, Recorded investment			$ (947)	$ (52)
Combination of Concession Types [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	4	1	13	6
Pre-modification, Recorded investment	$ 2,623	$ 1,156	$ 13,621	$ 3,238
Post-modification, Recorded investment	2,614	1,169	13,546	3,242
Financial effects of modification, Recorded investment	(9)	13	(75)	4
Financial effects of modification, Interest	$ (172)	$ (54)	$ (238)	$ (159)
Combination of Concession Types [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	13	1	25	6
Pre-modification, Recorded investment	$ 27,834	$ 31	$ 49,248	$ 25,075
Post-modification, Recorded investment	19,802	31	39,971	24,884
Financial effects of modification, Recorded investment	(8,032)		(9,277)	(191)
Financial effects of modification, Interest	$ (6)	$ (6)	$ (6)	$ (245)
Combination of Concession Types [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	9	10	27	22
Pre-modification, Recorded investment	$ 1,149	$ 1,296	$ 4,513	$ 2,551
Post-modification, Recorded investment	1,214	1,380	4,705	2,795
Financial effects of modification, Recorded investment	65	84	192	244
Financial effects of modification, Interest	$ (120)	$ (178)	$ (120)	$ (356)
Combination of Concession Types [Member] | Residential Limited Documentation [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	3	4	8	7
Pre-modification, Recorded investment	$ 392	$ 605	$ 1,704	$ 1,239
Post-modification, Recorded investment	493	662	1,872	1,298
Financial effects of modification, Recorded investment	101	57	168	59
Financial effects of modification, Interest	$ (123)	$ (91)	$ (462)	$ (121)
Combination of Concession Types [Member] | Home Equity Lines and Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification	22	22	76	41
Pre-modification, Recorded investment	$ 2,301	$ 2,003	$ 8,534	$ 3,555
Post-modification, Recorded investment	2,301	2,003	8,534	3,555
Financial effects of modification, Interest	$ (178)	$ (199)	$ (741)	$ (424)
Combination of Concession Types [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		25	8	42
Pre-modification, Recorded investment		$ 471	$ 85	$ 693
Post-modification, Recorded investment		471	85	693
Financial effects of modification, Interest		$ (17)	$ (3)	$ (28)
Combination of Concession Types [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		12	17	35
Pre-modification, Recorded investment		$ 117	$ 196	$ 384
Post-modification, Recorded investment		117	196	384
Financial effects of modification, Interest		$ (12)	$ (32)	$ (44)
Combination of Concession Types [Member] | Other Commercial Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification			1
Pre-modification, Recorded investment			$ 124
Post-modification, Recorded investment			$ 124
Other [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification			1
Pre-modification, Recorded investment			$ 4,723
Post-modification, Recorded investment			4,447
Financial effects of modification, Recorded investment			$ (276)
Other [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification				2
Pre-modification, Recorded investment				$ 8,991
Post-modification, Recorded investment				8,883
Financial effects of modification, Recorded investment				$ (108)
Other [Member] | Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		1		1
Pre-modification, Recorded investment		$ 267		$ 267
Post-modification, Recorded investment		$ 267		$ 267
Other [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		15	38	38
Pre-modification, Recorded investment		$ 93	$ 55	$ 134
Post-modification, Recorded investment		$ 93	$ 55	$ 134
Other [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification		5	5	12
Pre-modification, Recorded investment		$ 33	$ 45	$ 113
Post-modification, Recorded investment		$ 33	$ 45	$ 113
Interest Rate Reduction [Member] | Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification			1
Pre-modification, Recorded investment			$ 129
Post-modification, Recorded investment			129
Financial effects of modification, Interest			$ (25)
Interest Rate Reduction [Member] | Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification				1
Pre-modification, Recorded investment				$ 99
Post-modification, Recorded investment				99
Financial effects of modification, Interest				$ (19)
Interest Rate Reduction [Member] | Automobile [Member]
Financing Receivable, Modifications [Line Items]
Number of modifications | Modification				7
Pre-modification, Recorded investment				$ 137
Post-modification, Recorded investment				137
Financial effects of modification, Interest				$ (10)